Pneumatic driving device and the associated method for micro fluids

ABSTRACT

A pneumatic driving device and the associated method for micro fluids, wherein the pneumatic driving device for micro fluids is constructed by connecting a fluid pipe with a structure that is formed by two gas stream inlets, a gas stream fender, a gas stream flow path and a gas stream outlet. The suction, exclusion and stagnation for the micro fluids inside the fluid pipes can be accomplished by adjusting the flow rates of the gas streams into the device at the two gas stream inlets. In the invention, several pneumatic driving devices are connected to form a single recursive pneumatic driving device by the concept of recursion, and the micro fluids inside several fluid pipes can be controlled to mix or to separate through the recursive pneumatic driving device by adjusting the flow rates of the gas streams into the device at different gas stream inlets.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The invention relates to a driving device for micro fluids andespecially relates to a pneumatic driving device and the associatedmethod for micro fluids. By the concept of recursion, a recursivepneumatic driving device and its associated method for micro fluids canbe established.

[0003] 2. Related Art

[0004] Because of the recent development of biochips the relatedtechnologies in the field are becoming more important ever than before,and the micro-scale total analysis system (μTAS) for biochips has becomethe necessary key point to the design and analysis of biochips. Hence,the associated so-called micro fluid systems for biochips have become aserious research subject and are being studied extensively. The microfluid systems let the biochips completely function and can allow thebio-chemical substances inside the biochips mix and react with theexamined species entering into the biochips completely. They comprisemany micro fluid elements such as micro pumps, micro valves, micro fluidpipes and micro fluid mixers. In order to integrate these micro fluidelements to become a complete micro-scale total analysis system, new andinnovative structures and manufacturing processes for biochips should befurther studied.

[0005] Usually the micro fluid system has to separate the incoming microfluids into several parts, and in the mean time micro valves areconventionally utilized to separate the incoming micro fluids and toguide them into one of the following branch pipes. Micro valves areactive parts and have two disadvantages when they are in use, that is,they are more expensive and their performance is not so stable.Therefore, much research has been proposed to attempt to use passiveparts in constructing micro valves to overcome these disadvantages.Related research results about the micro fluid systems in the past, forexample the studies of micro pumps and micro fluid switchers, aredescribed as follows:

[0006] 1. On-chip built-in mechanical micro pump: this kind of micropump can be directly built on biochips by micro-machining technology andwith this design some movable parts should be set inside the biochips.Some proposed designs based on this concept are described as follows:

[0007] First is the electro-statically driven diaphragm micro pumpinvented by Roland Zengerle etc., (U.S. Pat. No. 5,529,465), wherein themain body of the micro pump comprises four layers of silicon substrate.Pumping action can be accomplished by the pulsating electrostaticattraction among the upper two silicon layers induced by supplying thespecific AC current (50V, 400 Hz) together with two passive checkvalves. The performed flow rate is about 350 μl/min.

[0008] The micro machined peristaltic pump invented by Frank T. Hartley(U.S. Pat. No. 5,705,018) is a more succinct design. With this designserial flexible conductive strips are placed on the inner walls of themicro pipes of the biochips and when the electric potential pulse wavesgo through above the micro pipes, the serial flexible conductive stripsare attracted by the electrostatic forces to move upward in sequence toform the peristaltic phenomenon of the micro pipes. Accordingly thisperistaltic phenomenon can be utilized to drive the micro fluids to flowinside the micro pipes. The phase of the applied electric potentialpulse waves must be carefully controlled and the peak value is about 100V. The performed flow rate is 100 μl/min.

[0009] The disadvantages of the above described on-chip built-inmechanical micro pumps are that the structures are too complicated, itis not easy to clean the micro pumps, and the manufacturing andassembling processes are difficult. These built-in mechanical micropumps cannot be used repeatedly when they are applied to test thechemical reagents because it is very difficult to completely clean them.So, a biochip is used only one time and then discarded, but this greatlyincreases production cost. Unfortunately for the on-chip built-inmechanical micro pumps and the on-chip built-in peristaltic pumpcomplicated manufacturing processes and/or costly specific materialsmust be utilized. Thus the production cost will be greatly increased,and of course, this result is contrary to the requirements of massproduction.

[0010] In 1998 Andrews S. Dewa and Christophe J. P. Servrain proposedthe design concept of remote actuators for micro fabricated fluidicdevices (U.S. Pat. No. 5,788,468), wherein the active movable parts(actuators) of micro pumps are replaced on the outside surroundingregions of the biochips. Inside the biochips are placed only the on-chipmovable members that are formed by LIGA technology and are similar topistons or turbines. The actuators placed outside the biochips can drivethe on-chip passive movable parts settled inside the biochips toreciprocate or to rotate in specific pump chambers to accomplish thepumping action. The focus of this proposed patent is that differentprecious on-chip movable parts can be easily established by LIGAtechnology and can be applied easily together with the associatedunsophisticated chambers to achieve the pumping action for micro fluids.Hence this invention has partially overcome the problem of the highproduction cost of one-time-use biochips. However, the question of howpower can be transmitted from the outside actuators to the on-chipmovable parts was not answered.

[0011] If the outside actuators are connected with the on-chip movableparts by levers, then the movable parts cannot be completely sealedinside the pumping chambers. It is reasonable that the requiredengineering specifications for the production of biochips must beenhanced so that the micro fluids cannot leak out of the pumpingchambers under the reciprocation of the movable parts and under the highpressure inside the pumping chambers. It was suggested in theabove-described patent to utilize the magnetic rotor device to drive themovable parts sealed completely inside the pumping chambers toaccomplish the pumping action by the electro-magnetic effects. Thissuggestion was also proposed by Kaluji Tojo and Yoshiaki Hirai in 1997for their invention “micro flow controlling pump” (U.S. Pat. No.5,599,175). However, specific and expensive materials must be utilizedto construct the magnetic pulp bodies as the movable parts.

[0012] 2. On-chip built-in electrode micro pump: this kind of micro pumpis not a mechanical micro pump and with this design it is not necessaryto set movable parts inside the micro pump. Conventional operatingprinciples for this kind of micro pump are classified in three differenttypes (electroosmosis EO, electrohydrodynamics EHD and electrophorosisEP) and will be described as follows:

[0013] The invention “apparatus and methods for controlling fluid flowin micro channels” (U.S. Pat. No. 5,632,876) proposed by Peter J.Zanzucci etc. in 1997 is a combinative application of electroosmosis andelectrohydrodynamics, wherein four electrodes classed among two pairsare interlaced inside the micro pipes of biochips. The inner pair ofelectrodes is set close to each other and both stretch into the microfluids inside the micro pipes. The current circuit can be formed by thispair of electrodes and the surrounding micro fluids around this pair ofelectrodes when a high voltage is supplied. At the same time thesurrounding micro fluids around this pair of electrodes is pushed tomove along the direction against the current direction. This phenomenonis the so-called Electrohydrodynamic pumping (EHD Pumping). The otheroutside pair of electrodes is placed a little farther away from eachother and only touch the pipe walls of the micro pipes. When hundreds tothousands of high voltages are supplied to the outside pair ofelectrodes, the pipe walls of the micro pipes are firstly electricallycharged, then negative and positive electric charges gather on thematerial surfaces where the positive and negative electrodes are,respectively, and consequently when the micro fluids contain negativeelectric particles, these particles are attracted toward the directionto the negative electrode, which is filled with positive electriccharges. The micro fluids are also attracted toward to the positiveelectrode, which is filled with negative electric charges. Theabove-described phenomenon is the so-called Electroosmosis pumping (EOpumping). The focus of this proposed invention is to combine andintegrate these two different pumping phenomena with different pumpingdirections to accomplish the pumping actions for micro fluids and theguiding controls for micro fluids like propelling action, expellingaction and stagnate action. The working micro fluids for electroosmosismust be polar solutions containing electrically charged particles, whilefor electrohydrodynamics they must be non-polar solutions or organicsolutions. This invention claims that after the integration of these twodifferent phenomena the methods proposed can be applied for all microfluids whether they are polar or non-polar.

[0014] In 1997 Paul C. H. Li and D. Jed Harrison proposed another methodunder their thesis: transport, manipulation and reaction of biologicalcells on-chip using electrokinetic effects (Anal. Chem. 69,154-158),which is a combined application of electroosmosis and electrophorosis.The working principle of electrophorosis is rather simple and isdescribed as follows: the electrical charged particles of solutions aredirectly attracted by electrodes and their direction of motion isagainst that induced by electroosmosis. However, the focus of thisinvention is that the electrical charged particles of solutions areattracted by both the electroosmosis and the electrophorosisto effectsbut the solutions are not. Therefore the principle contribution of thisinvention is to drive the canine erythrocytes existing inside thesolutions but not the micro fluids. From the experiments it shows thatthe canine erythrocytes can easily be guided. Their direction of motioncan be changed by the attractive force differences of the electroosmosisand the electrophorosis effects occurring among the interlaced micropipes.

[0015] The disadvantage of the above described on-chip built-inelectrode micro pumps is that there are too many restrictions for theapplication when in use. But from the manufacturing perspective it canbe seen that the structure of the electrode micro pumps is the simplestand the production cost is lowest. However, as discussed before, thereare too many restrictions for the application when in use:

[0016] The micro pipes must be filled with solutions in advance andhence it is not possible to fill examined species or reactive reagentsinto the empty micro pipes at first.

[0017] The EHD pump can only drive the micro fluids to move for a shorttime while the EO and EP pumps are mainly utilized to drive electricallycharged particles of micro fluids and have no influence on the movementsof micro fluids. Consequently, the pumping effect induced by theabove-mentioned three micro pumps is not significant for micro fluids,and the performed flow rates are about 10 μl/min. Furthermore, thedriving forces of these three different micro pumps can function only invery narrow micro pipes (the diameter of the micro pipes is about 100μm) and very high voltages (hundreds to thousands of volts) must besupplied across a very short distance. Therefore, the operating cost ishigh.

[0018] The EHD pumps can only be applied for non-polar organic solutionswhile the EO and EP pumps are only adequate for polar solutionscontaining charged ions. The ion concentration of solutions willseriously affect the pumping efficiency of these kinds of micro pumps.Thus it is difficult to guide and control the motions of micro fluidswhen the incoming examined species and reactive reagents have complexcompositions or the ion concentration changes in the reacting processes.

[0019] 3. On-chip external servo system: this concept is the simplestway to overcome the above-mentioned problems and obviously there is noneed to set active parts inside the biochips. Thus the structure of thiskind of system is rather unsophisticated and the production cost is alsorather low. It is also not necessary to use the micromachiningtechnologies to construct the external servo systems and the externalservo systems can be utilized repeatedly because they are not in directcontact with the examined species and reactive reagents. Thus it may beproper to utilize this kind of system to examine the reactions ofbiochemical substances and reagents for one-time-use biochips. However,with this design perspective another problem of the world-to-chipinterface will occur, that is, the connection between the transmissionpipes under ordinary scale (transmitted micro fluids may be gases orreagents) and the biochips under micro scale can only be achieved by anumber of complicated micromachining technologies.

[0020] In 1998 N. J. Mourlas et al. proposed their thesis “novelinterconnection and channel technologies for micro fluids, Proceedingsof the μTAS'98 Workshop, 1998, 27-30”, in which differentinterconnections between transmission pipes and biochips were shown.From the design perspective of this thesis it can be clearly seen thatthe pressure inside the micro pipes increases rapidly when micro fluidsare poured into the micro pipes or into the micro reactive chambers ofbiochips. Accordingly strict requirements for the connections betweenthe transmission pipes and the biochips should be satisfied (leakagetest: 60 psi, pull test: 2N). Conventional epoxy substances should beapplied to enhance the connections between the transmission pipes andthe biochips. From the above-described design perspective theorientation and location points of the transmission pipes should befirstly defined by DRIE technology and then the polyoxymethyleneplastics are applied to form the couplers of the transmission pipes byinjection modeling. Although the transmission pipes can just be insertedinto biochips by the couplers, it is recommended to reheat thetransmission pipes to 250° C. in order to establish more reliableconnections.

[0021] For the biochips applied to examine biochemical reactions thestructures and the manufacturing processes of the on-chip built-inmechanical micro pumps are too sophisticated and their production costis too high. For the on-chip built-in electrode micro pumps there aretoo many restrictions for application and their pumping efficiency isnot significant. If the problem of the world-to-chip interface can beovercome with the on-chip external servo system then this would be thebest way to utilize the servo systems used repeatedly as the guidingelements for micro fluids together with the biochips that are only usedone time and have no active parts.

[0022] 4. Pneumatic micro pump having no junctions: Dr. Yuo proposedthis design, which uses simple pneumatic servo systems providingdifferent driving gas streams with different modes. Guiding motion,expelling motion and stagnation motion of micro fluids inside the micropipes in the internal regions of the micro reactive module can beaccomplished when the driving gas stream with a specific mode flowsthrough the airway of the micro reactive module.

[0023] 5. Pressure difference driven pneumatic micro switch for microfluids: this was proposed by Brody in 1998 and has three or morereservoirs containing pressured gas. The pressure in the junction of thereservoirs is regulated to equal that of the third pipe. The microfluids are controlled to flow from the first channel to the secondchannel. The disadvantage of this design is that it is inconvenient toutilize this micro switch because all reservoirs must be connected tothe air supplies independently. Pollution easily occurs if there are nofixed outward blowing gas streams when the biochips are in use.

SUMMARY OF THE INVENTION

[0024] In consideration of the above-mentioned problems the principalaim of the invention is to provide a pneumatic driving device and theassociated method for micro fluids by controlling the gas flowvelocities to control the flow directions of micro fluids.

[0025] A second aim of the invention is to provide a pneumatic drivingdevice and the associated method for micro fluids that are constructedby the external servo system together with the one-time-use biochiphaving no active parts. A gas stream power transmission method is usedto drive the micro fluids of the biochip, such that there is no need toform any connection between the external servo system and the biochip.Hence the complicated problem of the world-to-chip does not occur.

[0026] In order to achieve these objects the invention provides apneumatic driving device and the associated method for micro fluids,which includes a pair of gas streams, an gas stream flow path structureand an gas stream flow path. The pair of the gas streams have acontrollable flow rate and injection flow direction. The gas stream flowpath structure formed by two gas stream inlets, a solitary gas streamfender, a gas stream flow path, a gas stream outlet, and a fluid pipe.The pair of gas streams enters the driving device at the two gas streaminlets, goes through the gas stream fender and the gas stream flow path,and flows out of the driving device at the gas stream outlet. The fluidpipe is connected with the gas stream flow path structure and thesuction, the exclusion and the stagnation of one of the micro fluidsinside the fluid pipe can be accomplished by adjusting the injectionflow rates into the gas stream flow path structure of the pair of gasstreams.

[0027] The connection between the fluid pipe and the gas stream flowpath structure is formed as an outfall in the shape of an invertedtriangular, a connective gas stream flow path having a big open mouth ora connective fluid pipe having a small open mouth. The form of the gasstream fender may be an arbitrary combination of a triangle, a square, acircle and a polygon. The position of the gas stream fender may be onthe upper region of the outfall or near the outfall. The other end ofthe fluid pipe is the injection inlet for micro fluids.

[0028] The invention provides a recursive pneumatic driving device andthe associated method for micro fluids. The recursive pneumatic drivingdevice is constructed by the recursive combination of theabove-mentioned inventive pneumatic driving devices. Therefore, themicro fluids inside several micro fluid pipes can be driven andcontrolled to separate, to mix or to change flow directions.

[0029] Further detailed technical embodiments of the invention aredescribed together with the drawings as follows.

[0030] Further scope of applicability of the invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWING

[0031]FIG. 1 is a schematic drawing of the pneumatic driving device formicro fluids of the invention;

[0032]FIG. 2 is a schematic drawing of the recursive pneumatic drivingdevice for micro fluids of the invention;

[0033]FIG. 3 illustrates the embodiment of the recursive pneumaticdriving device for micro fluids of the invention;

[0034] FIGS. 4A-4G illustrate the first operating experiments of therecursive pneumatic driving device for micro fluids of the invention;

[0035] FIGS. 5A-5G illustrate the second operating experiments of therecursive pneumatic driving device for micro fluids of the invention;and

[0036] FIGS. 6A-6C illustrate the third operating experiments of therecursive pneumatic driving device for micro fluids of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention proposes a guiding device with no valves for microfluids, which directly apples the different velocities in the differentlayers of the gas streams determined by the Navier-Stokes equation offluid mechanics together with a simple structure design to createdifferent viscous forces to exert on the micro fluids. The guidingaction and the exclusion for micro fluids can be accomplished by thesedifferent viscous forces. By applying this proposed guiding device withno valves together with the recursive structure the flow directions ofmicro fluids inside several micro pipes can be controlled.

[0038]FIG. 1 shows a first embodiment of the pneumatic driving devicefor micro fluids of the invention 10. The device comprises the first gasstream inlet 11, the second gas stream inlet 12, the gas stream flowpath 13, the gas stream outlet 14, the gas stream fender 15, the micropipe 16 and the injection inlet for reagents 17. The operatingprinciples of the device are described as follows:

[0039] As shown in FIG. 1, because of the gas stream fender 15 thesuction force exerted on the micro fluids inside the micro pipe 16 canbe accomplished when the gas stream enters the device at the first gasstream inlet 11, goes through the gas stream flow path 13, and flows outof the device at the gas stream outlet 14. The intensity of this suctionforce depends on the velocity of the gas stream. When the gas streamenters the device at the second gas stream inlet 12, goes through thegas stream flow path 13, and flows out of the device at the gas streamoutlet 14, the exclusion force exerted on the micro fluids inside themicro pipe 16 can be accomplished by the gas stream fender 15. Theintensity of this exclusion force is also dependent on the velocity ofthe gas stream. Consequently, the flow direction (down to up or up todown) and the flow velocity (a velocity limit is associated) of themicro fluids inside the micro pipe 16 can be controlled by controllingthe velocities of the gas streams entering at the first and second gasstream inlets. Computer programs can be applied to simulate themagnitudes and effects of the suction and exclusion forces, that is, thevelocities of the micro fluids.

[0040] The whole operating procedures are described as follows: firstlythe liquid examined species are injected via the reagents into thedevice at the injection inlet 17 and then the liquid examined speciesfill the micro pipe 16. Secondly the flow directions and the velocitiesof the examined species inside the micro pipe 16 can be controlled bycontrolling the velocities of the gas streams at the first gas streaminlet 11 and the second gas stream inlet 12 such that the required fluidpower can be provided to operate the biochips passively.

[0041] By extending the above-addressed operating principles and theconcept of recursion a recursive pneumatic driving device for microfluids (as shown in FIG. 2) can be established. By this proposedrecursive pneumatic driving device for micro fluids not only can theflow directions of the micro fluids be controlled and guided into twodifferent directions, but also the micro fluids can be controlled toseparate and the shunt ratio can be controlled. Two pneumatic drivingdevices shown in FIG. 1 are utilized to form the embodiment of therecursive pneumatic driving device 20 shown in FIG. 2, which comprisesthe first gas stream inlet 201, the second gas stream inlet 202, thethird gas stream inlet 203, the first gas stream flow path 204, thesecond gas stream flow path 205, the gas stream outlet 206, the firstgas stream fender 207, the second gas stream fender 208, the first micropipe 209, the second micro pipe 210, the third micro pipe 211 and theinjection inlet for reagents 212.

[0042] As shown in FIG. 2, the first pneumatic driving device for microfluids is constructed by the second gas stream inlet 202 and the thirdgas stream inlet 203 while the second pneumatic driving device for microfluids is constructed by the first gas stream inlet 201 together withthe second and third gas stream inlets 202 and 203, respectively.

[0043] The operating principles and the actions of the first pneumaticdriving device for micro fluids are the same as those described inFIG.1, that is, the gas streams enter the device at the second gasstream inlet 202 and at the third gas stream inlet 203, go through thesecond gas stream fender 208, and are applied as the sources for suctionand exclusion forces. The operating principles and actions of the secondpneumatic driving device for micro fluids are also similar to thosediscussed in FIG. 1. The only one difference is that the second gasstream inlet 202 and the third gas stream inlet 203 are utilized andtreated together as the common gas stream inlet. That is, whether thegas streams enter the device at the second gas stream inlet 202 or atthe third gas stream inlet 203 and go through the second gas streamfender 208, they will cause the suction force (the force from up todown) exerted on the micro fluids inside the second micro pipe 210. Thegas stream that enters the device at the first gas stream inlet 201causes the suction force for the micro fluids inside the second micropipe 210 after it goes through the first gas stream fender 207.

[0044] Whether the force exerted on the micro fluids inside the thirdmicro pipe 211 is a suction force or a exclusion force depends on theforces exerted on the micro fluids inside the first micro pipe 209 andthe second micro pipe 210. That is, the motions of the micro fluidsshould be calculated by the Navier-Stokes equation of fluid mechanics.

[0045] Therefore, the confluence and anti-confluence of micro fluids canbe accomplished through the proposed recursive pneumatic driving devicefor micro fluids by supplying two gas streams. That is, the micro fluidsinside the third micro pipe 211 shown in FIG. 2 are controlled to flowinto the first micro pipe 209 and the second micro pipe 210 separately,and the anti-confluence ratio of micro fluids into these two micro pipescan be controlled to achieve the value from 0% to 100%. Conversely, themicro fluids inside the first micro pipe 209 and the second micro pipe210 can also be controlled to mix into the micro pipe 211.

[0046] Based on the above description the whole operating procedure ofthe proposed invention will be explained as follows: firstly the liquidexamined species are injected into the device at the injection inlet 212through the reagents and the third micro pipe 211 is filled with theliquid examined species. Secondly, the velocities and the flowdirections of the liquid examined species inside the third micro pipe211 can be controlled so that they are directed into the first micropipe 209 and/or into the second micro pipe 210 simultaneously. This isdone by controlling the flow velocities of the gas streams at the firstgas stream inlet 201, the second gas stream inlet 202 and the third gasstream inlet 203. When the examined species are inside the first micropipe 209 or the second micro pipe 210, their flow directions can becontrolled by altering the flow velocities of the gas streams at thefirst gas stream inlet 201, the second gas stream inlet 202 and thethird gas stream inlet 203 such that the required fluid power for theoperations of the biochips can be passively supplied.

[0047] The forms of the gas stream fender 15, the first gas streamfender 207 and the second gas stream fender 208 shown in FIGS. 1 and 2are shaped as a “solitary inland” and can be established by arbitrarycombinations of triangles, squares, circles and polygons.

[0048] The connection between the fluid pipe and the gas stream flowpath shown in FIG. 1 is shaped as an outfall 18 and is utilized toconnect the fluid pipe and the gas stream flow path. Similarly, theoutfalls 213 and 214 are established in the connection between the fluidpipe and the gas stream flow path shown in FIG. 2. The shapes of theoutfalls can be a triangle, a connective gas stream flow path having abig open mouth or a connective fluid pipe having a small open mouth. Thegas stream fenders can be set in the upper region of the outfall or nearthe outfall.

[0049] In addition, in order to find out the values of the suction andexclusion forces exerted on each of the micro pipes, the simulationprogram CFD-ACE+ can be applied and utilized to find out the adequategas stream flow rates, and then based on the simulated flow rates theactual flow rates are adjusted to meet the requirements.

[0050] FIG.3 shows the first embodiment based on the design of FIG. 2,wherein the blank regions are the fillisters. The material used is aPMMA block with the scale of 100*100*50 mm. The widths of the three gasstreams inlets are 3 mm, 1 mm and 1 mm, respectively, and the scale ofthe other structures are defined as the scale shown in the figure. Thedigging depths of all the structures are 1 mm, and the second PMMA blockis bored in order to connect it to the micro pipes of the first block;the bored hole is the injection inlet for the micro liquids. The twoPMMA blocks are connected to each other and the gas stream inlets aredug and bored once more with a lager diameter in order to connect themwith the gas stream pipes. After completing all the procedures describedabove the embodiment of the invention can be accomplished as shown inFIG. 3.

[0051] A pneumatic source or pump will be supplied and connected withthree parallel flow meters. These three flow meters are connected withthe three gas stream inlets of the two PMMA blocks, respectively, andhence the experimental setup can be established.

[0052] The detailed operating procedures of the invention will bedescribed as follows: firstly some color ink (for example the blue ink)is dropped into the device so that it is easier to observe and photo theexperimental results. Secondly, as shown in FIGS. 4A to 5G, the colorink is carefully controlled to flow inside each of the micro pipesrepeatedly. Based on the prior simulated results, the flow ratesmeasured by the three flow meters must be carefully controlled. Everyexperimental condition must also be carefully controlled so that thecolor ink can flow inside the micro pipes if the micro pipes have novalves. As shown in FIGS. 4A to 4G, the color ink can flow from thethird micro pipe to the second micro pipe (Q1=16 LPM, Q3=1.2 LPM, asshown in FIGS. 4A to 4C), continuously flows from the second micro pipeto the first micro pipe (Q2=4.1 LPM, as shown in FIGS. 4C to 4E), andfinally flows from the third micro pipe to the pipe 3 (Q2=3.2 LPM,Q3=1.4 LPM, as shown in FIGS. 4E to 4G). Therefore a whole loop motionis established.

[0053] Refer to FIGS. 5A to 5G for the second flow situation. Firstlythe color ink flows from the third micro pipe to the first micro pipe(Q1=19 LPM, Q2=4.2 LPM, Q3=0.5 LPM, as shown in FIGS. 5A to 5C),continuously flows from the first micro pipe to the second micro pipe(Q1=16 LPM, Q2=0.7 LPM, Q3=1.4 LPM, as shown in FIGS. 5C to 5E), andfinally flows from the second micro pipe to the third micro pipe (Q2=4.9LPM, Q3=1.1 LPM, as shown in FIGS. 5E to 5G). Therefore another wholeloop motion is established.

[0054] Refer to FIGS. 6A to 6C for the procedures to control the microfluids to flow into different micro pipes. FIGS. 6A to 6C show that thecolor ink flows separately into two parts when it flows through thebranch of the third micro pipe. These two separate parts of color inkflow independently into the first and second micro pipes. Theseparations of the micro fluids inside the first micro pipe or insidethe second micro pipe can also be accomplished by controlling thevelocities of the gas streams at the gas stream inlets.

[0055] The pneumatic driving device and the associated method for microfluids proposed by the invention is clearly different from the pneumaticmicro pump having no junctions proposed by Dr. Yuo. The characteristicsof the pneumatic micro pump having no junctions proposed by Dr. Yuo arethat the gas stream fender is connected with the main body of the micropump and is set after the outfall. But from the invention the gas streamfender is formed as a “solitary inland”. That is, it is isolated fromthe main body of the device and is set in front of the outfall. Thetriangle gas stream fender can be utilized to make the micro fluids flowrepeatedly inside the micro pipes, and the concept of recursion (thesuperposition) is applied to guide the micro fluid inside the three ormore micro pipes to mix or to separate.

[0056] The pneumatic driving device and the associated method for microfluid proposed by the invention is also clearly distinct from thepressure difference driven pneumatic micro switch for micro fluidsinvented by Brody. In comparison with that proposed Brody it is clearthat structure of the invention is quite simple as it is not necessaryto control and adjust the three pneumatic supplies because only twopneumatic supplies need to be adjusted to meet the requirements. Theparameters that need to be adjusted are only the flow velocities of thegas streams, and this point is significantly distinct from Brody'sinvention. Furthermore, there is a fixed outward blowing gas stream inthe invention that will not pollute easily when this design is used forbiochips.

[0057] The other advantages of the invention are the designs of the“solitary inland” triangle gas stream fender and the outfall, and thereare no movable parts of the device. Only via the different suction andexclusion effects induced by the structure itself and by the regulationsof the injection positions and the injection flow rates of the gasstreams are the required motions of the micro fluids controlled.

[0058] By extending the triangle gas stream fender of the invention andthe associated method for micro fluids together with the concept ofrecursion, the flow motions of the micro fluids can be completelycontrolled even if the micro pipes have two or more branches.

[0059] All the gas streams designed by the invention are designed toblow outward and thus the examined species or the reactive reagentsinside the micro reactive module do not pollute the servo systems.

[0060] The working principles of the invention have no relation with thepolarities or the ion concentrations of the driven micro fluids andconsequently the applicability of the invention is rather extensive.

[0061] To summarize, the invention provides a microstructure having asimple structure, easy manufacturing processes and low production cost.It can be directly applied to control the flow motions of micro fluidsby adjusting the injection positions and the injection flow rates of gasstreams without any micro fluid valves.

[0062] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A pneumatic driving method for micro fluids, comprising the followingsteps: providing a group of gas streams, each having a controllable flowrate and injection direction; providing a matched gas stream flow pathstructure having a “solitary inland” gas stream fender for receivingsaid group of gas streams; providing a fluid pipe to connect said gasstream flow path structure; and adjusting the injection flow rates ofsaid pair of gas streams into said gas stream flow path structure todrive one of the micro fluids inside said fluid pipe for sucking,excluding and stagnating.
 2. The pneumatic driving method of claim 1,wherein said pair of gas streams are composed of two gas streams havingspecific flow directions and flow rates.
 3. A recursive pneumaticdriving method for micro fluids, comprising the following steps:providing a group of gas streams, each having a controllable flow rateand injection direction; providing a matched gas stream flow pathstructure containing a “solitary inland” gas stream fender for receivingsaid group of gas streams; providing a fluid pipe connected to said gasstream flow path structure, wherein said fluid pipe having a first, asecond, and a third pipes connected by an intersection; and adjustingthe flow rates of said pair of gas streams entering said gas stream flowpath structure to drive the micro fluid inside said fluid pipes forsucking, excluding and stagnating, and to drive the micro fluid formixing, separating or turning flow directions inside said first, secondand third pipes.
 4. The recursive pneumatic driving method of claim 3,wherein said pair of gas stream are selected from the group consistingof one portion, two portions and three portions of gas streams.
 5. Therecursive pneumatic driving method of claim 3, wherein the separatedpath of said micro fluid is selected from the group consisting of: themicro fluid flowing separately from said first pipe into said second andthird pipes, the micro fluid flowing separately from said second pipeinto said first and third pipes, and the micro fluid flowing separatelyfrom said third pipe into said first and second pipes.
 6. The recursivepneumatic driving method of claim 3, wherein the flow loop of said microfluid is selected from the group consisting of the following loops: fromsaid first pipe, to said second pipe, said third pipe and then saidfirst pipe in sequence; from said first pipe, to said third pipe, saidsecond pipe and then said first pipe in sequence; from said third pipe,to said first pipe, said second pipe and then said third pipe insequence; from said third pipe, to said second pipe, said first pipe andthen said third pipe in sequence; from said second pipe, to said firstpipe, said third pipe and the second pipe in sequence; from said secondpipe, to said third pipe, said first pipe and then said second pipe insequence.